test: detect if we're running inside gdb and disable forking

The Check test framework forks by default which is annoying when running gdb.
Try to detect whether we're inside gdb by ptracing ourselves. If that works,
we're not inside a debugger. If it doesn't, then assume we're inside a
debugger and set CK_FORK to "no".

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

2 files changed, 40 insertions, 2 deletions

diff --git a/libevdev/libevdev.h b/libevdev/libevdev.h
index 37ca2f4..f5ceda0 100644
--- a/libevdev/libevdev.h
+++ b/libevdev/libevdev.h
@@ -177,8 +177,9 @@ extern "C" {
  *     git grep "suite_create"
  *     git grep "tcase_create"
  *
- * By default, check forks, making debugging harder. Run gdb as below to avoid
- * forking.
+ * By default, Check forks, making debugging harder. The test suite tries to detect
+ * if it is running inside gdb and disable forking. If that doesn't work for
+ * some reason, run gdb as below to avoid forking.
  *
  *     sudo CK_FORK=no CK_RUN_TEST="test case name" gdb ./test/test-libevdev
  *
diff --git a/test/test-main.c b/test/test-main.c
index 73d79c9..91128c3 100644
--- a/test/test-main.c
+++ b/test/test-main.c
@@ -22,6 +22,10 @@
 
 #include <config.h>
 #include <check.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/ptrace.h>
+#include <sys/wait.h>
 
 extern Suite *event_name_suite(void);
 extern Suite *event_code_suite(void);
@@ -31,9 +35,42 @@ extern Suite *libevdev_has_event_test(void);
 extern Suite *libevdev_events(void);
 extern Suite *uinput_suite(void);
 
+static int
+is_debugger_attached(void)
+{
+	int status;
+	int rc;
+	int pid = fork();
+
+	if (pid == -1)
+		return 0;
+
+	if (pid == 0) {
+		int ppid = getppid();
+		if (ptrace(PTRACE_ATTACH, ppid, NULL, NULL) == 0) {
+			waitpid(ppid, NULL, 0);
+			ptrace(PTRACE_CONT, NULL, NULL);
+			ptrace(PTRACE_DETACH, ppid, NULL, NULL);
+			rc = 0;
+		} else
+			rc = 1;
+		_exit(rc);
+	} else {
+		waitpid(pid, &status, 0);
+		rc = WEXITSTATUS(status);
+	}
+
+	return rc;
+}
+
+
 int main(int argc, char **argv)
 {
 	int failed;
+
+	if (is_debugger_attached())
+		setenv("CK_FORK", "no", 0);
+
 	Suite *s = libevdev_has_event_test();
 	SRunner *sr = srunner_create(s);
 	srunner_add_suite(sr, libevdev_events());